It is known to oxidize phenol to p-benzoquinone in the presence of copper catalysts; see for example U.S. Pat. No. 3,987,068. Improvements to these copper catalyzed oxidations of phenol to p-benzoquinone have been disclosed and claimed in U.S. Ser. No. 284,893, filed July 20, 1981, and U.S. Ser. No. 339,965, filed Jan. 18, 1982, which disclosures are hereby incorporated by reference.
Heretofore, p-benzoquinone has been converted to hydroquinone by use of various catalysts. Thus, for example, Sabatier passed quinone vapors mixed with hydrogen over a reduced copper catalyst (e.g., a heterogeneous vapor phase system) to obtain hydroquinone (Comptes rendus Ac. Sc. vol. 146, p. 457, 1908 and vol. 172 p. 733, 1921), but in this process the catalyst has a very limited life. R. Cornubert and J. Phelisse, Compt. Rend. 229, 460 (1949) disclose use of Raney nickel to convert quinone to hydroquinone. U.S. Pat. No. 2,495,521 discloses nickel, cobalt, or copper catalyzed heterogeneous vapor phase hydrogenation of benzoquinone in the presence of steam. Popova et al., Chem. Abs. 53,275 (1959) disclose hydrogenation of benzoquinone with nickel, platinum and palladium--calcium carbonate. M. Calvin, J. Am. Chem. Soc., 61, 2230 (1939) discloses use of a copper-quinoline complex derived from cuprous acetate to promote hydrogenation of purified quinone, but this process is limited in that, at most, only one-half mole of hydrogen is taken up per mole of the Copper I--quinoline complex and thus the hydrogenation is very inefficient and perhaps not catalytic. Also of interest is the disclosure of Yananaka et al., Bull. Inst. Phys. Chem. Research (Tokyo) 14, 31 1935 which reduces quinones to oxy compounds with copper and Al.sub.2 O.sub.3 -promoted nickel.